Pressure regulator having single strut seat with strut coaxial to plunger

ABSTRACT

A pressure regulator including a housing including an inlet flow passage and an outlet flow passage; a plunger reciprocally mounted in the housing and including a plunger flow passage having an axis offset from an axis of the inlet flow passage, and a stationary valve seat fixed to the housing and positioned between the inlet flow passage and an inlet to the flow passage of the plunger, wherein the valve seat is configured to receive and abut the inlet to the flow passage of the plunger.

RELATED APPLICATION

This is a continuation application to U.S. patent application Ser. No.14/252,035, filed Apr. 14, 2014.

BACKGROUND OF INVENTION

The invention relates to pressure regulators and particularly topressure regulators for supplying water to irrigation sprinklers andnozzles.

Irrigation systems often have several sprinklers and nozzles arrangedalong an extended water supply pipe. For example, a water supply pipe ina center pivot irrigation system may extend a quarter to half a mile(400 to 800 meters). The water supply pipe may have a diameter of six toten inches (152 to 254 millimeters) and provide water for over a hundredsprinklers arranged along the pipe. Each sprinkler is typicallyconnected to the water supply pipe by a smaller water pipe that extendsvertically and includes a pressure regulator.

The sprinklers are typically designed to receive water under arelatively low pressure and within a narrow pressure range. Pressureregulators reduce the pressure in the water supply pipe to a pressuresuitable for a sprinkler or nozzle. The pressure regulator ensures thatthe water pressure is within the design range of the sprinkler ornozzle.

The elevation of the water supply pipe in an irrigation system rises andfalls as the pipe travels over the hills and low points of anagricultural field. These changes in elevation vary the pressure in thewater supply pipe. The pressure regulators adjust to the changes inpressure such that water flows to the sprinklers and nozzles at arelatively uniform pressure.

Nelson Irrigation Corporation of Walla Walla, Wash., U.S.A.,manufactures and sells flow-through type pressure regulators having atubular housing with an inlet at one end and an outlet at the other end.Pressure loss through the regulator is controlled by a gap between avalve seat and a tubular plunger in the regulator. The tubular plungeris biased away from the valve seat in a normally open condition by acompression spring. The pressure of the flow at the outlet of theregulator acts on a diaphragm in the regulator. The diaphragm isattached to and moves with the plunger.

Within a normal operating flow rate range, the spring force balancesagainst the outlet pressure applied to the diaphragm. This balance setsthe opening between the valve seat and the plunger to cause the desiredpressure loss at the flow rate demanded by the sprinkler. An increase inthe inlet pressure will initially increase the pressure at the outletand thus increase the pressure on the diaphragm. Due to the pressureincrease, the diaphragm moves the tubular plunger towards the valve seatto narrow the gap and reduce the pressure at the outlet of theregulator. The counteracting forces of the spring and the outlet flowpressure move the plunger and adjust the gap to achieve a substantiallyuniform outlet pressure of the flow leaving the pressure regulator.

The valve seat and a strut(s) supporting the valve seat tend to collectdebris from the water flow. Water for the sprinklers is often drawn fromponds and irrigation ditches near agricultural fields. The water isdirty with suspended grasses, other plant material and other debris. Thegrass and other fibrous debris can wrap around and collect on the valveseat and its support strut(s). Debris collecting on the valve seat andstrut obstructs the flow through the regulation gap and can interferewith the movement of the plunger. The debris can impair the operation ofthe pressure regulator, causing the pressure of the output flow to varyfrom the desired output pressure, reducing the rate of flow through thepressure regulator, and causing excessive pressure losses through theregulator.

Efforts to prevent debris from collecting on the valve seat and strutinclude having a cantilever-beam type single strut which is less likelyto collect debris than multiple struts. See U.S. Pat. Nos. 7,048,001 and7,140,595 and U.S. Patent Publication 2012/0285561. While a single struthas been successful in suppressing the collection of debris on the strutand valve seat, there remains a continuing problem of debris collectingon or near the strut and valve seat in a pressure regulator.

A pressure regulator having an adjustable valve seat is shown in U.S.Pat. No. 7,401,622, wherein the valve seat is substantially offset fromthe flow passage so that the valve seat may function as an On-Off valve.Shifting the seat to such an extent resulted in extreme turns in thewater passage near the valve seat and inlet to the plunger. The extremeturns tend to cause excessive pressure losses and nonuniform flow at theoutlet. Thus, there is a continuing need to reduce pressure losses inpressure regulators and for the regulators to discharge water in a flowthat has a relatively uniform velocity profile.

BRIEF SUMMARY OF THE INVENTION

A pressure regulator has been conceived having a valve seat that isoffset from the direction of flow through the regulator. The offsetshifts the valve seat and the strut supporting the valve seat towardsthe sidewall of the inlet casing and slightly out of the center of theflow passage. The offset allows for a more uniform expansion of the flowpassage surrounding the valve seat and strut, as compared to the flowpassage surrounding a strut and valve in a conventional regulator inwhich the plunger is coaxial with the inlet flow passage. The enlargedflow passage has an increased hydraulic diameter which results in lowerfrictional pressure losses of water flowing through the regulator andprovides an enhanced flow passage around the valve seat and strut andinto the plunger.

The shift of the valve seat and strut reduces the radial dimension ofthe strut and allows the strut to be more closely associated, e.g.,integrated, with the sidewall of the regulator housing. By reducing theradial dimension of the strut that extends into the flow passage, theforce moment applied by the water flow to the strut is reduced. Thestrut may have a generally triangular shape with a vertical leg of thetriangle attached to the sidewall, a horizontal leg extending to thevalve seat and a sloped leg extending downstream from the sidewall tothe valve seat. The sloped leg faces the water flow. Debris slides downthe sloped leg and does not catch on the strut. The strut may also havea generally cylindrical section that extends towards the plunger.

The strut may include a post extending downstream into the chambersurrounding the strut and valve seat. The post may extend from aninterior sidewall of the regulator housing. The strut may be connectedto the wall of the housing along an extended length of the wall. Theextended connection and shape of the strut form a strong support for thevalve seat. The strut is in contrast to the traditional cantileveredstrut which is subject to bending forces applied by the water flow.

The triangular brace shape of the strut allows the strut to beintegrated into the inlet housing. The inlet strut and valve seat may beformed as a single plastic injection molded component utilizingcollapsible core or unwinding core molding technology. In a conventionalpressure regulator, the inlet casing is typically formed separately fromthe strut and valve seat.

A pressure regulator has been conceived comprising a housing includingan inlet flow passage and an outlet flow passage; a plunger reciprocallymounted in the housing and including a plunger flow passage having anaxis offset from an axis of the inlet flow passage and a stationaryvalve seat fixed to the housing and positioned between the inlet flowpassage and an inlet to the flow passage of the plunger, wherein thevalve seat is configured to receive and abut the inlet to the flowpassage of the plunger.

The offset may be an angular offset between the axis of the plunger flowpassage and the axis of the inlet flow passage, wherein the angularoffset, as determined by testing, is in a range of three to twelve andone-half degrees. Further, the axis of the inlet flow passage is coaxialwith an axis of the outlet flow passage, and the axis of the plungerflow passage intersects the axis of the inlet flow passage proximate tothe outlet of the flow passage in the plunger.

The stationary valve seat in the pressure regulator may be integral withthe inlet cap of the housing. The valve seat may be formed within or atthe end of a strut attached to an interior wall of the housing. Thestrut may include an upstream surface sloping out radially in adownstream direction along the entire length of the surface from theinterior wall to a nose of the strut. The nose of the strut may includea distal circumferential edge, bisected by a radical axis defined by theintersection of the inlet passage's cylindrical envelope and the valveseat circumference's elliptical projection normal to the inlet axis. Thestrut may also include a downstream cylindrical section coaxial with theaxis of the plunger.

The housing for the pressure regulator may include an inlet cap and anoutlet cap, and the strut is integral with the inlet cap. The inlet cap,valve seat and strut may be a single plastic component. Further, vane(s)may be positioned between the strut and an interior surface of thehousing to direct water through the regulator, and mitigate vortexingflow conditions in the flow chamber around the seat's strut.

In another embodiment, the pressure regulator may comprise a housingincluding an inlet cap having an inlet flow passage and an outlet caphaving an outlet flow passage; a tubular plunger reciprocally mounted inthe housing; a flow passage including the inlet flow passage, theplunger and the outlet flow passage; a stationary valve seat connectedto the housing and positioned between the inlet flow passage and aninlet to the plunger, wherein the valve seat is configured to receiveand abut the inlet to the plunger, and a strut supporting the valveseat, wherein the strut is integral with the inlet cap. The stationaryvalve seat, a strut supporting the seat and the inlet cap may be formedas a single component by plastic injection molding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the inlet and side of a pressureregulator.

FIG. 2 is a perspective view of the inlet and side of the pressureregulator shown in cross section.

FIG. 3 is an exploded view of the pressure regulator showing eachcomponent in cross section.

FIG. 4 is a side view showing the pressure regulator in cross sectionwith the plunger retracted.

FIG. 5 is a side view showing the pressure regulator in cross section,with the plunger advanced against the valve seat.

FIG. 6 is a side view of the inlet cap of the pressure regulator incross section.

FIG. 7 is a perspective view of the inlet cap with a portion of theinlet cap cut away.

FIG. 8 is an end view showing the outlet end of the inlet cap.

FIG. 9 is an end view showing the outlet end of an inlet cap having aninternal vane to direct water flow.

FIG. 10 is an enlarged end view of the inlet end of the inlet cap,normal to line of sight.

FIG. 11 is a perspective view of another inlet cap with a portion of theinlet cap cut away.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 3 show a flow-through type pressure regulator 10 inperspective, cross-sectional and exploded views respectively. Thepressure regulator 10 includes a housing formed by an inlet cap 12 andan outlet cap 14. The inlet and outlet caps are connected by an annularretainer 16 that engages a ring ledge 18 on the inlet cap and includes athreaded inner surface 20 that engages a threaded outer surface 22 onthe outlet cap. The threaded outer surface 22 may be cylindrical or anannular series of legs, as shown in FIG. 3. Similarly, the inlet cap mayhave legs that interleave with the legs of the outlet cap when the capsare clamped together by the retainer. The inlet cap 12, outlet cap 14and retainer 16 form the housing of the pressure regulator.

The inlet cap 12 includes an inlet flow passage 24, and the outlet cap14 includes an outlet flow passage 26. Ribs 25 on the inlet and outletcaps provide structural support for the inlet and outlet flow passages.The inlet and outlet flow passages may have threaded surfaces to receivewater pipes (not shown) connected to the pressure regulator. The waterpipe connected to the inlet flow passage provides water under pressureto the pressure regulator from a water supply pipe. A vertical waterpipe (not shown) typically connects the pressure regulator to the watersupply pipe. The outlet flow passage 26 may be connected to a sprinklerassembly that hangs or is otherwise supported by the pressure regulator.

The retainer 16 securely holds together the inlet cap 12 and the outletcap 14. A secure connection between the inlet cap and outlet cap isneeded to support the sprinkler assembly, avoid leakage of water fromthe pressure regulator and avoid separation of the pressure regulator.The retainer 16 may include an annular array of teeth 23 to engage teeth21 (FIGS. 1 & 7) on the outer surface of the inlet cap. The engagementbetween the teeth locks the retainer to the inlet cap. The retainer 16may be replaced by bolts and nuts, or other fasteners, that securetogether the inlet cap and outlet cap.

FIGS. 4 and 5 show the pressure regulator 10 in cross section. FIG. 4shows a wide gap 27 in the flow passage through the regulator. FIG. 5shows a substantially closed gap 27 that blocks the water passage. Thepressure regulator 10 reduces the water pressure to maintain a constantwater pressure in the outlet flow passage 26, regardless of the waterpressure in the inlet flow passage 24.

To maintain a uniform outlet water pressure, the pressure regulator 10widens or narrows the gap 27 depending upon the outlet water pressure.The gap 27 is the most constricted portion of the flow passage in thepressure regulator. The width (see double arrow in FIG. 4) of the gap 27adjusts automatically in response to the outlet water pressure. The gap27 is widest while the water pressure in the outlet flow passage 26 isno greater than a prescribed pressure level. The prescribed pressurelevel may be set during the design of the pressure regulator and isdictated by the rate of the spring (also known as the spring constant).The gap 27 narrows (FIG. 5) if the water pressure in the outlet flowpassage 26 exceeds the prescribed pressure. Narrowing the gap 27 resultsin a corresponding reduction in water pressure at the outlet of theregulator.

The gap 27 is formed between an inlet 28 to a tubular plunger 30 and astationary valve seat 32. The size of the gap 27 is determined by theaxial position of the plunger inlet 28 relative to the valve seat 32. Anannular section or circular disc of the valve seat is sized to receivethe circular inlet 28 to the plunger to close the gap. The plunger 30includes a cylindrical plunger passage 34 for water flowing between theinlet flow passage 24 and the outlet flow passage 26. The plunger 30moves along its axis 36 within a short range of distances. The range ofdistances that the plunger moves corresponds to the gap 27. The range isevident by comparing the plunger position in FIG. 4 with the plungerposition in FIG. 5. The movement of the plunger advances or retracts itsinlet 28 towards and away from the valve seat 32.

A helical spring 38 biases, e.g., pushes, the plunger towards the outletcap 14 and away from the valve seat 32. Water pressure in the outletflow passage 26 is substantially the same as the water pressure in thediaphragm chamber 39 because there is fluid communication around andthrough the damper O-ring 47 and gland 45 which seats the O-ring. Thewater pressure in the diaphragm chamber pushes the plunger towards thevalve seat by acting on an effective annular area of the diaphragm 40attached to the plunger. While the pressure in the diaphragm chamber 39is at or below the prescribed pressure level, the spring force appliedto the plunger and diaphragm is greater than the force due to waterpressure applied to the diaphragm. The side of the diaphragm opposite tothe outlet flow passage may be at an ambient pressure, which is achievedby venting the liner 66 to the atmosphere through vent holes in theliner and through a torturous path provided by the retainer's buttressthread 20.

As the water pressure at the diaphragm chamber 39 increases beyond theprescribed pressure, the pressure applied to the diaphragm 40 overcomesthe spring force and moves the plunger 30 towards the valve seat 32 tonarrow the gap 27. The narrowing of the gap 27 reduces the waterpressure in the diaphragm chamber 39. The reduced water pressure lessensthe pressure applied to the diaphragm 40 and allows the spring 38 toretract the plunger 30 to widen the gap 27. The offsetting spring forceand water pressure determine the width of the gap 27 and regulate thewater pressure at the diaphragm chamber 39.

An O-ring 47 is fitted loosely within the downstream plunger guide bore49 and retained in an annular gland 45 on the downstream end of theplunger 30. The O-ring may be fitted to allow approximately 0.007 to0.015 inches (0.178 to 0.38 millimeters) of radial clearance within theguide bore 49.

A shallow axial bleed groove(s) 51 may be formed in connection with orbetween the O-ring 47 and the gland 45 on the plunger to providepressure communication between the outlet flow passage 26 and thediaphragm chamber 39. The axial bleed grooves 51 may have a depth of0.005 to 0.010 inches (0.127 to 0.254 millimeters). The axial bleedgrooves may be symmetrically arranged within the gland 45 or formed onthe inner cylindrical surface of the bore 49. The bleed grooves may alsobe formed between ribs on the O-ring 47. At normal operation, both theradial clearance and axial bleed groove(s) provide fluid communicationbetween the outlet flow passage 26 and an annular chamber 39 between thediaphragm and an inner surface of the outlet cap 14.

A sudden inlet pressure surge will cause the O-ring 47 to compress in anaxial direction and deform the O-ring outward diminishing the radialclearance between the ring and the bore 49. The deformation of theO-ring creates a friction that slows the axial movement of the plunger30 toward the seat 32. While the O-ring is deformed, the radialclearance reduces to zero and the axial bleed groove provides theprimary fluid communication to the diaphragm chamber. Reducing theradial clearance and increasing friction between the O-ring and boreprevents a resonance in the movement of the plunger.

Because the axial bleed grooves ensure that there is always some fluidcommunication with the diaphragm chamber, a hydraulic lock in thediaphragm chamber does not form. As the pressure surge subsides, theO-ring 47 returns to its free shape which restores the radial clearanceand allows the plunger to more easily slide in the bore. The spring 38,diaphragm 40 and other components of the regulator are designed, in aconventional manner, to achieve a desired water pressure at the outletof the regulator 10.

The diaphragm 40 may be an annular, flexible skirt secured to theplunger between a diaphragm retainer 41 and a plunger flange 43. Thediaphragm retainer 41 may slide over the tube of the plunger and snapinto a groove around the circumference of the tube. The plunger flange43 may be integral with the tube of the plunger. Before the diaphragmretainer 41 is snapped in place on the tube of the plunger, thediaphragm 40 is placed between the plunger flange and diaphragmretainer. The diaphragm is secured between the diaphragm retainer 41 andplunger flange 43, by snapping the diaphragm retainer on the tube of theplunger. The diaphragm is secured to the housing of the pressureregulator by being clamped between the downstream rim 67 (FIG. 3) of theliner and an annular rim 69 in the outlet flow cap 14.

The plunger 30 has an axis 36 offset from the axis 42 of the inlet flowpassage 24. The offset may be an angular offset 44 in a range of aboutthree to twelve and one-half degrees. Test indicates that angularoffsets in a range of three to eight degrees, such five degrees, provideoptimal regulator performance by minimizing turbulence and nonuniformflow at the outlet of the regulator, suppressing clogging of the gap bydebris and minimizing pressure losses through the regulator. The plungeraxis 36 projects into the inlet flow passage 24.

The plunger axis 36 may intersect the axis 42 of the inlet cap near thedownstream end 46 of the plunger 30. Offsetting the plunger axis 36 iscontrary to the conventional approach that aligns the axis of theplunger with the axes of the inlet and outlet flow passages.Intersecting the plunger axis 36, the end of the plunger aligns theoutlet of the plunger with the outlet flow passage, where the outletaxis 50 is coaxial with the inlet flow axis 42.

The axis 50 of the outlet flow passage 26 may be coaxial to the axis 42of the inlet flow passage 24. Having these axes 42, 50 coaxial minimizesforce moments applied to the pressure regulator by the inlet and outletwater pipes attached to the regulator. Having these axes 42, 50 coaxialalso assists in achieving vertical alignment along the inlet pipe,pressure regulator, outlet water pipe and the sprinkler. A sprinklertypically works best, e.g., projects a symmetrical water spray pattern,if its rotational axis is vertical.

FIGS. 6, 7 and 8 illustrate the inlet cap 12 in a cross-sectional view,perspective view with a portion of the cap cut away and an end view,respectively. The plunger 30 and annular seal retainer 56 are shown bydotted lines to illustrate the gap 27 and a chamber 48 of the flowpassage surrounding the valve seat 32 and strut 54.

The strut 54 may be a single strut having an upstream surface 58, a nose60, and a back surface 62 that is generally parallel to the plunger axis36. The nose 60 and back surface 62 may form a generally cylindricalpost section of the strut extending downstream into chamber 48. Theupstream surface 58 of the strut slopes from the sidewall 52 of theinlet cap 12. The side edges of the upstream surface 58 extend to theback surface 62 of the strut. The strut may be embodied with variousshapes including the generally triangular shape attached to the sidewalland downstream post shown in FIG. 2. For example, the post section ofthe strut may be more pronounced than shown in FIG. 2. The strut extendsdownstream into the chamber 48, which is in contrast to conventionalcantilevered-beam struts that extend solely radially into the flowstream.

The upstream surface 58 of the strut may be smooth with a slight convexcross-sectional shape in a direction parallel to the plunger axis 36.The upstream surface 58 of the strut facing the water flow is at a steepslope, such as at an angle in a range of twenty-five to fifty-fivedegrees. The steep slope of the upstream surface 58 deflects debris offthe strut and into a gap (W1) of the flow chamber 48. Debris reachingthe upstream surface 58 is swept by the water flow along the upstreamsurface and off the nose 60 of the strut.

The chamber 48 is formed between the sidewall 52 of the chamber 48, theouter surfaces of the valve seat 32 and strut 54, and the upper surfaceof an annular seat retainer 56. Water enters the chamber 48 from theinlet flow passage 24 and leaves the chamber by flowing into the plungerinlet 28. The chamber 48 surrounds the valve seat 32 and strut 54, andhas a larger cross section than the cross section of the inlet flowpassage 24. The large cross section of the chamber 48 provides arelatively large volume of water to flow over and around the strut 54and into the inlet flow passage 24. The distance (W1) between the nose60 (also the front) of the strut and the sidewall 52 may besubstantially the same as the distance (W2) between the back of thestrut and the sidewall 52. The large chamber 48 and the substantiallyequal distances (W1, W2) between the strut 54 and the sidewall 52provide an open flow passage that is substantially free of areas ofstagnant flow in the chamber where debris may accumulate. Further, thechamber 48 is free of radially projecting spokes, beams, ribs, vanes andother radially extending supports conventionally used for a valve seat.

Offsetting the plunger axis 36 allows the strut 54 and valve seat 32 tobe shifted down into the expanded chamber 48. Due to the shift, thevalve seat and strut may be positioned closer to and integrated with thethreaded sidewall 52 of the inlet flow passage 24, as compared to aconventional cantilever beam strut extending radially to the center ofthe flow passage.

The strut and valve seat may be shifted sufficiently away from the inletaxis 42 such that a line of sight 63 (FIG. 4) exists through the inletflow passage, the plunger and the outlet flow passage. The line of sightrepresents an unobstructed flow path through the inlet cap, plunger, andoutlet cap when the plunger is in its fully or substantially open state.

FIG. 10 is an enlarged view of the upstream surface 58 and nose 60 ofthe strut. A lune 61 is formed by the overlap of the inlet and outletflow passages 24, 26, wherein the lune 61 is not obstructed (fully orpartially) by the strut 54. The line of sight 63 in FIG. 4 extendsthrough the lune 61. The significance of the line of sight 63 and thelune 61 is to illustrate that shifting the strut and valve seat forms amore open and less obstructed flow passage through the regulator thanoccurs when the strut and valve seat are centered in the flow passage.Increasing the openness and reducing obstructions in the flow passageshould reduce the frictional pressure loss in the regulator and reducethe tendency of debris to clog the flow passage.

The flow path through the inlet flow passage 24, through the chamber 48and into the plunger 30 is relatively uninterrupted and smooth. The flowpath may be free of radially extending support beams, ribs and spokesthat, if present, could disrupt the flow. The sloping upstream surface58 of the strut 54 extends from the sidewall of the inlet flow passage24 to the chamber 48 and further to the nose 60 of the strut.

The upstream surface 58 of the strut starts in or at the end of theinlet flow passage 24 and is upstream of the chamber 48. The upstreamsurface 58 starts radially inward of the sidewall of the chamber 48 dueto the angular offset 44 and as shown in FIG. 4. The upstream surface 58directs water into the chamber and around the strut. A portion of thewater flowing from the inlet flow passage 24 directly enters the chamber48, and does not directly contact the strut. Another portion of thewater flows over and around the upstream surface 58 to enter the chamberand around the back surface 62. As evident from FIGS. 6 and 7, and acomparison of FIGS. 8 and 10, the projected area of the upstream surface58 on a plane perpendicular to the axis of the inlet passage is smallerthan the area within the circumference of the valve seat 32.

Water from the inlet flow passage 24 enters the chamber 48. Much of thewater flows through the front region (W1) of the chamber 48 and into theplunger while avoiding the strut. Avoiding the strut reduces the amountof turbulence created as the water flows through the chamber 48. Waterthat flows over the upstream surface 58 of the strut may be deflectedinto the plunger or may flow to the chamber back region (W2) behind thestrut. The water in the back region gap (W2) flows to gap 27 and intothe plunger. The shape of the chamber 48 and the relatively largeregions (W1, W2) and the bowl shape of the upstream surface of theannual seal retainer 56 contribute to minimizing turbulence and flowvelocity variations in the water flowing through the chamber 48 and intothe plunger.

A vane 64 (FIG. 9) in the region (W2) may be used to direct the flowtowards the plunger and reduce turbulence in the flow. The vane 64 isoptional and is not shown in the embodiments in FIGS. 1 to 8. The vane64 may be integral with the inlet cap and fixed to an overhang 76between the back surface 62 of the strut and the sidewall 52 of thechamber. The vane deflects water flowing around the strut towards theplunger. The vane may be a planar rib, have an inverted V-shape oranother shape that deflects water towards the plunger.

The relatively large flow volume in the chamber 48 tends to reducefrictional losses in the water pressure. The frictional pressure lossmay be less than five (5) pounds per square inch (34 kPa) while thepressure regulator is operating at a maximum water flow. The reductionin the frictional pressure loss is due, in part, to the relatively highhydraulic diameter of the chamber 48. The hydraulic diameter is theratio of the cross-sectional area of the chamber 48 and the total lengthof the wetted perimeter of the chamber 48 and the strut at said crosssection.

Turbulence and velocity variations in the flow entering the plungersettle out as the water flows through the plunger passage. A plungerpassage 34 having a flow length equal to at least five diameters of thepassage is generally sufficient to settle turbulence and velocityvariations. The length of the plunger may also be selected such thataxis 36 of the plunger intersects the axis 50 of the outlet flow passage26 in the outlet cap.

The annular seal retainer 56 rests in an annular recess in the sidewall52 of the inlet casing and seats on a tubular liner 66 for the spring38. The inlet end of the plunger 30 extends through a center circularopening in the seal retainer 56. The upstream surface of the sealretainer has a bowl shape with gradually curved walls to direct watertowards the inlet 28 of the plunger. The center circular opening of theseal retainer 56 is coaxial with and adjacent a dynamic O-ring seal 68that fits around the inlet of the plunger.

The O-ring seal 68 is dynamic in that the plunger moves reciprocallyagainst the O-ring. The dynamic O-ring seal 68 and a static O-ring seal70 seat in annular grooves on the upstream face 72 of the liner 66. TheO-ring seals 68, 70 prevent higher pressure water in the chamber 48 fromseeping between the plunger and the liner 66 and sidewall 52.

The strut 54 may have a generally triangular shape and a downstream postas is shown in FIG. 6. The apex of the triangle is integrated with theinlet cap and is aligned with the sidewall of the inlet flow passage 24.The legs of the triangle are formed by the upstream surface 58 and theback surface 62 of the strut. The triangular shape provides a strongsupporting brace for the valve seat 32, which is at the base of thetriangle. A triangular brace shape is suited to support the valve seatand withstand a water flow, especially as compared to a conventionalcantilevered beam strut.

As shown in FIG. 8, the valve seat 32 may be an annular surface 78 in aplane parallel to the inlet 28 of the plunger. A raised ridge 80 at thecircumference of the annular surface 78 guides the plunger inlet 28 tothe annular surface. The valve seat and strut may be generally hollowwith supporting ribs 82 forming an X-brace within the hollow area of thestrut.

FIG. 11 is a perspective view of an inlet cap 100 for an alternativepressure regulator 90 having a plunger 92 with an axis offset by abouttwelve and one-half degrees from the axis of the inlet passage. Thelarge angular offset shifts the valve seat 102 and seat post 104 nearlyentirely out of the inlet flow passage 106. The seat post 104 is thesupport strut for the valve seat.

The seat post 104 forms a support post for the valve seat 102. The seatpost 104 is substantially a cylindrical post projecting downstream froman overhang section 108 of the sidewall of the inlet cap 100. The seatpost 104 may be integral with the inlet cap. The inlet cap, with thestrut and valve seat, may be formed as a single component by plasticinjection molding, utilizing unwinding core technology. The upstreamsurface 110 of the strut is on the side of the cylindrical strut. Theupstream surface 110 may be shaped to blend the strut with the overhangsection 108 or to direct water flow down into a chamber 112 downstreamof the inlet flow passage 106 and upstream of the inlet to the plunger92. The upstream surface 110 may be formed from the unwinding coreforming inlet flow passage 106.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

We claim:
 1. A pressure regulator comprising: a housing assembly including an inlet flow passage and an outlet flow passage; a plunger reciprocally mounted in the housing assembly; a plunger flow passage extending through the plunger having an inlet open to the inlet flow passage and an outlet open to the outlet flow passage, wherein an axis of the plunger flow passage is offset from an axis of the inlet flow passage, and a stationary valve seat fixed to the housing assembly, wherein the stationary valve seat extends into a flow passage defined by the inlet flow passage and the inlet to the plunger flow passage, and the stationary valve seat is configured to receive and abut the inlet of the plunger.
 2. The pressure regulator of claim 1 wherein the housing assembly includes a first housing section that includes the inlet flow passage and a second housing section that includes the outlet flow passage, and the stationary valve seat and the first housing section are a single-piece component.
 3. The pressure regulator of claim 1 further comprising an annular diaphragm coupling the plunger to the housing assembly, wherein the diaphragm forms a deformable seal between the outlet flow passage and a chamber in the housing assembly.
 4. The pressure regulator of claim 1 further comprising a strut supporting the stationary valve seat and attached to an interior wall of the inlet flow passage, wherein the interior wall is within the housing assembly and the strut extends downstream from the interior wall to the stationary valve seat.
 5. The pressure regulator of claim 4 wherein the strut includes a region forming an upstream surface sloping in a downstream direction along the entire length of the upstream surface from the interior wall to a nose of the strut.
 6. The pressure regulator of claim 5 wherein the strut includes a downstream cylindrical section coaxial with the axis of the plunger.
 7. The pressure regulator of claim 1 wherein the housing assembly includes an inlet cap and an outlet cap, and the strut, valve seat and inlet cap are a single piece component.
 8. The pressure regulator of claim 7 wherein the strut, valve seat and inlet cap are a single plastic component.
 9. The pressure regulator of claim 4 further comprising a vane extending from the strut towards an interior surface of the housing assembly.
 10. The pressure regulator of claim 1 wherein the inlet flow path is devoid of radially extending support beams, ribs and spokes.
 11. The pressure regulator of claim 1 wherein the valve seat includes a valve seat surface facing the inlet of the plunger, and a center of the valve seat surface is offset from the axis of the inlet flow passage.
 12. The pressure regulator of claim 1 further comprising a chamber within the housing assembly and between the inlet flow passage and the plunger, wherein the valve seat is within the chamber, and a distance between a wall of the chamber and one edge of a downstream surface of the valve seat equals a distance between an opposite edge of the downstream surface of the valve seat and the wall of the chamber.
 13. The pressure regulator of claim 12 wherein the one edge of the downstream surface of the valve seat is at a nose of the valve seat.
 14. The pressure regulator of claim 1 wherein the axis of the plunger flow passage projects into the inlet flow passage.
 15. The pressure regulator of claim 1 wherein the valve seat includes a downstream valve seat surface and an upstream surface facing the inlet flow passage, wherein a projected surface area of the upstream surface as projected on a plane perpendicular to the axis of the inlet flow passage is less than an area within a perimeter of the valve seat surface.
 16. A pressure regulator comprising: a housing assembly including an inlet cap having an inlet flow passage and an outlet cap having an outlet flow passage; a tubular plunger reciprocally mounted in the housing assembly and defining a plunger flow passage extending through the plunger; a flow passage including the inlet flow passage, a plunger flow passage, and the outlet flow passage; a stationary valve seat fixed to and immobile with respect to the inlet cap, wherein the stationary valve seat is configured to receive and abut the inlet to the plunger; and a strut supporting the stationary valve seat, wherein the strut and the inlet cap are a single piece component, wherein an axis of the tubular plunger is offset from an axis of the inlet flow passage.
 17. The pressure regulator of claim 16 wherein the inlet cap and strut are a pressure-injected molded plastic component.
 18. The pressure regulator of claim 16 further comprising an annular diaphragm coupling the plunger to the housing assembly, wherein the diaphragm forms a deformable seal between the outlet flow passage and a chamber in the housing assembly.
 19. The pressure regulator of claim 16 wherein the inlet cap includes an interior wall defining the inlet flow passage and the strut includes a region having an upstream surface sloping in a downstream direction along the entire length of the upstream surface from the interior wall to a nose of the strut.
 20. The pressure regulator of claim 16 wherein the strut includes a downstream cylindrical section coaxial with the axis of the plunger.
 21. The pressure regulator of claim 16 further comprising a vane extending from the strut towards an interior wall surface of the housing assembly.
 22. The pressure regulator of claim 16 wherein the inlet flow path is devoid of radially extending support beams, ribs and spokes.
 23. The pressure regulator of claim 16 wherein the valve seat includes a valve seat surface facing the inlet of the plunger, and a center of the valve seat surface is offset from the axis of the inlet flow passage.
 24. The pressure regulator of claim 16 further comprising a chamber within the housing assembly and between the inlet flow passage and the plunger, wherein the valve seat is within the chamber, and a distance between a wall of the chamber and one edge of a downstream surface of the valve seat equals a distance between an opposite edge of the downstream surface of the valve seat and the wall of the chamber.
 25. The pressure regulator of claim 24 wherein the one edge of the downstream surface of the valve seat is at a nose of the valve seat.
 26. The pressure regulator of claim 16 wherein the axis of the plunger flow passage projects into the inlet flow passage.
 27. The pressure regulator of claim 16 wherein the valve seat includes a downstream valve seat surface and an upstream surface facing the inlet flow passage, wherein a projected surface area of the upstream surface as projected on a plane perpendicular to the axis of the inlet flow passage is less than an area within a perimeter of the valve seat surface. 